Mumps virus is a common human pathogen that frequently invades the central nervous system(CNS). Strains of mumps virus differ in their cytopathogenicity (the degree of cytopathology that they cause in vitro) and their neurovirulence (the ability to invade the CNS and infect neurons) and there appears to be a correlation between the in vitro and in vivo biological effects. The molecular basis for these strain-dependent differences is not known and is the focus of the proposed experiments. Preliminary evidence suggests that the strain-dependent differences in cytopathogenicity and neurovirulence result at least in part, from differences in the structures of the virus surface glycoproteins which mediate virion binding to host cells, the cell to cell spread of infection and which are the primary targets of the host's immune response. The proposed experiments are designed to characterize the structures of the surface glycoproteins of mumps virus using biochemical and immunochemical techniques and to identify functional domains that contribute to cytopathology in vitro and neurovirulence. Specifically, a panel of monoclonal antibodies (MCAs) will be used to study the antigenic structures of the surface glycoproteins of a representative strain of mumps virus. The glycoproteins will be characterized further by mapping their peptide fragments and by determining their amino acid sequences. Neutralizing MCAs with distinct reactivity patterns will then be used to isolate mumps virus variants that differ from the parental mumps virus strain by only minor alterations in the structure of the surface glycoprotein to which the selecting, MCA binds. The structural alterations will be defined at the level of the glycoprotein's amino acid sequence for those mumps virus variants that differ from the parental mumps virus strain in in vitro and in vivo biological effects; in this way, the changes in primary structure that correlate with a modification in glycoprotein function will be identified. Finally, an attempt will be made to generate specific polyclonal antibodies against putative functional domains of the surface glycoproteins by using as immunogens synthetic peptides with sequence homology to selected regions of the intact glycoproteins. These antibodies will then be tested for activity in in vitro functional assays and for a protective effect in the newborn hamster model of mumps meningoencephalitis. It is anticipated that the results of these studies will contribute significantly to the understanding of the pathogenesis of mumps virus infection of the CNS and provide the theoretical basis for the development of a synthetic peptide mumps vaccine.